Electronic visual display signs have become commonplace in sports stadiums, arenas, and other public forums throughout the world. These signs can be in a variety of sizes, ranging from small signs measuring just a few inches per side to stadium scoreboards that measure several hundred square feet in size. Electronic visual display signs are assembled and installed using a series of smaller panels, each of which are themselves further comprised of a series of modules. The modules are internally connected to each other by a bus system. A computer or central control unit sends graphic information to the different modules, which then display the graphic information as images and/or text on the sign.
Each module in turn is made up of hundreds of individual light-emitting elements, or “pixels.” In turn, each pixel is made up of a plurality of light-emitting points (e.g., one red, one green, and one blue). The light-emitting points are termed “subpixels.” During calibration of each module, the color and brightness of each pixel is adjusted so the pixels can display a particular color at a desired brightness level. The adjustment to each pixel necessary to create a color is then stored in software or firmware that controls the module.
Although each module is calibrated during production, the individual subpixels often do not exactly match each other in terms of brightness or color because of manufacturing tolerances. Display manufacturers have tried to remedy this problem by binning subpixels for luminance and color. However, this practice is both expensive and ineffective. The acute ability of the human eye to detect contrast lines in both luminance and color makes it very difficult to blend two modules that were manufactured with subpixels from different binning lots. Furthermore, the electronics powering various modules have tolerances that affect the power and temperature of the subpixels, which in turn affects the color and brightness of the individual subpixels. As the modules age, the light output of each subpixel may degrade.